Abundance of non-target pests in transgenic Bt-maize: A farm scale study

Abstract

Abstract. The impact of transgenic Bt-maize, expressing the Cry1Ab protein, on aphids, leafhoppers, cutworms and wireworms was evaluated at the farm scale by comparing their abundance on Bt-plots and those sown with the isogenic variety over three consecutive growing seasons. The impact of Bt-maize was different on each of the three-herbivore groups. There were significantly more aphids on the Bt-maize but in terms of aphid species, the difference was only statistically significant for Sitobion avenae and not for the other three most abundant species (Metopolophium dirhodum, Rhopalosiphum padi and Macrosiphum euphorbiae). The analysis of aphid age structure showed consistently more individuals on Bt-plots; differences were significant for alates, apterous adults and young nymphs of R. padi, apterous adults and apterous fourth instar nymphs of S. avenae, alates, apterous adults and apterous fourth instar nymphs of M. dirhodum. Leafhoppers (Zyginidia scutellaris), particularly mature nymphs, were also more abundant on the Btmaize. In spite of this there was no difference in leafhopper damage to Bt and non Bt-maize. The reasons for this are unclear but may be due to changes in Bt-maize that favoured aphids and leafhoppers. Differences in aphid and leafhopper densities were not high enough to affect yield. However, they may have affected the availability of prey for polyphagous predators such as Orius sp. The Btmaize did not affect the incidence of cutworms (Agrotis segetum) or wireworms (Agriotes lineatus). These results indicate that Btmaize does not have a negative impact on the non-target maize biocenosis at the farm scale.

Diversity of carabid beetles (Coleoptera: Carabidae) under three different control strategies against European corn borer in maize

“…Similarly to spiders and harvestmen (Řezáč et al 2006), we could not detect any treatment effect on the assemblage of carabid beetles in any of the study fields. Our results are thus congruent with previous findings (Volkmar & Freier 2003;Candolfi et al 2004;Pons et al 2005;Eizaguirre et al 2006;Farinos et al 2008;Balog et al 2011), including those from the Czech Republic. No significant negative effect of Bt maize on carabid beetles, rove beetles, and spiders was found in the study from south-easten part of the Czech Republic (Habuštová et al 2006) nor significant differences between Bt maize and izogenic cultivar were found in the occurrence of aphids, thrips, and predatory bugs (Sehnal et al 2004).…”

“…In most cases, assemblages of epigeal arthropods seemed not to be affected by presence of transgenic Bt maize (Volkmar & Freier 2003;Candolfi et al 2004;Sehnal et al 2004;Habuštová et al 2005Habuštová et al , 2006Pons et al 2005;Eizaguirre et al 2006;Farinos et al 2008;Balog et al 2011; but see Wold et al 2001), and these results were repeated also for Bt cotton and vegetables (Leslie et al 2007;Torres & Ruberson 2007). Indeed, some authors conclude that compared to conventional farming, the use of transgenic plants enhances arthropod biodiversity in crop fields via reduced input of insecticides to the system (Ferry et al 2006;Leslie et al 2007).…”

The effect of Cry1AB insecticidal protein on the incidence of entomopathogenic fungi infecting aphids on Bt maize

“…The vast majority of studies indicate no effect of such varieties on aphids. In most cases laboratory investigations concluded that aphids could not be affected because the toxin is not transported in the phloem sap on which these insects feed (Raps et al, 2001;Pons et al, 2005). However, there are also a few reports relating different GM plants, mentioned in introduction, pointing to the prospective, indirect action on these herbivores and their natural enemies (Lumbierres et al, 2004;Burgio et al, 2011;Stephens et al, 2012).…”

Request from the European Commission to review scientific studies related to the impact on the environment of the cultivation of maize Bt11 and 1507 ‐ Scientific opinion of the Panel on Genetically Modified Organisms

“…Even though aphid performance fell within the normal variation observed among conventional maize varieties, different studies reported that aphids perform better on Bt-maize than on near isogenic counterparts (e.g., Bourguet et al, 2002;Dutton et al, 2002;Lumbierres et al, 2004;Pons et al, 2005;Eizaguirre et al, 2006). With the larger colony densities of aphids on Bt-maize, more honeydew was produced, in turn increasing parasitoid longevity and rate of parasitism.…”